The present invention relates to a variable displacement swash plate compressor.
Japanese Laid-Out Patent Publication No. 52-131204 describes a conventional variable displacement swash plate compressor (hereafter simply referred to as the compressor). The compressor has a housing including a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores. A rotatable drive shaft is supported in the housing. A swash plate that is rotatable together with the drive shaft is arranged in the swash plate chamber. A link mechanism is located between the drive shaft and the swash plate to allow the inclination angle of the swash plate to change. The inclination angle refers to an angle relative to a direction orthogonal to the rotation axis of the drive shaft. Each cylinder bore accommodates a piston. The piston reciprocates in the cylinder bore and defines a compression chamber in the cylinder bore. A conversion mechanism coverts rotation of the swash plate to reciprocation of the piston in each cylinder bore. The stroke when the piston reciprocates is in accordance with the inclination angle of the swash plate. The inclination angle of the swash plate is changed by an actuator, which is controlled by a control mechanism.
The actuator is rotatable integrally with the drive shaft in the swash plate chamber. More specifically, the actuator includes a partitioning body fixed to the drive shaft. The partitioning body accommodates a movable body, which is movable relative to the partitioning body along the rotation axis. A control pressure chamber is defined between the partitioning body and the movable body to move the movable body with the pressure of the control pressure chamber. A communication passage, which is in communication with the control pressure chamber, extends through the drive shaft. A pressure control valve is arranged between the communication passage and the discharge chamber. The pressure control valve is configured to change the pressure of the control pressure chamber and move the movable body relative to the partitioning body along the rotation axis. The movable body includes a rear end that is in contact with a hinge ball. The hinge ball, which is located at the central portion of the swash plate, pivotally couples the swash plate to the drive shaft. A spring, which urges the hinge ball in the direction that increases the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
A link mechanism includes the hinge ball and an arm, which is located between the partitioning body and the swash plate. The spring urges the hinge ball from the rear and keeps the hinge ball in contact with the movable body. A first pin, which extends in a direction orthogonal to the rotation axis, is inserted to the front end of the arm. A second pin, which also extends in a direction orthogonal to the rotation axis, is inserted to the rear end of the arm. The swash plate is supported by the arm and the two pins to be pivotal to the partitioning body.
In the compressor, a pressure regulation valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the movable body toward the rear and pushes the hinge ball toward the rear against the urging force of the spring. Thus, the swash plate pivots to decrease its inclination angle and shorten the stroke of the pistons. This decreases the compressor displacement for each rotation of the drive shaft.
When the pressure regulation valve closes and disconnects the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as the swash plate chamber. This moves the movable body toward the front, and the hinge ball follows the movable body due to the urging force of the spring. Thus, the swash plate pivots in a direction opposite to when the inclination angle of the swash plate decreases. This increases the inclination angle of the swash plate and lengthens the stroke of the pistons.
In the conventional compressor described above, the actuator is adapted to decrease the pressure of the control pressure chamber and increase the inclination angle of the swash plate. Thus, it is difficult to promptly increase the compressor displacement.